The electromagnetic vibration exciter usually comprises a fixed base, a magnetic circuit, a moving component, a guiding device, a suspension system and so on. With the development of the science and technology, the electromagnetic exciters are constantly required to output a vibration signal with a larger and larger displacement amplitude. For example, at a low frequency or even an ultralow frequency, the exciter should output a vibration signal with the displacement amplitude of 1000 mm in order to obtain a large signal-to-noise ratio. The long-stroke vibration exciter raises new requirement for the property of the elastic suspension device.
An electromagnetic vibration exciter generally uses mechanical elastic suspension devices, such as metal spring leaf or rubber tubes, etc. to support and restore the moving component. When the operating stroke of the exciter is relatively small, the mechanical elastic suspension device operates in a linear zone, whose effect on the accuracy of the output waveform of the exciter is negligible. When the operating stroke of the exciter is relatively large (for example, when working at an ultralow frequency up to 0.01 Hz, the exciter could output a vibration signal with the displacement amplitude of up to 1000 mm), the mechanical elastic suspension device will exhibit relatively large nonlinear characteristics, which will have a relatively large impact on the exciter performance. Besides, the larger the displacement amplitude of the exciter is, the smaller the stiffness of the mechanical elastic suspension device should be. However, in order to reduce the effect of the zero drift of the moving component and the environmental noise, the dampness of the suspension device should be relatively large. It is difficult to design such type of mechanical elastic suspension device with small stiffness and large dampness. In addition, due to that the material characteristics of the mechanical elastic suspension device change always with time, the positional accuracy cannot be repeatable. Finally, when the installation of the mechanical elastic suspension device is finished, its stiffness and damping parameters cannot be modified freely any more. For these reasons, the mechanical elastic suspension device cannot meet the requirement arisen with the continuous development of electromagnetic exciters, especially for the long-stroke electromagnetic exciter.